Many components used for subterranean wells, such as wells for production of oil or gas or injection wells, have the basic form of tubulars with bores. Due to pressure handling and safe production, such bores must be able to be opened and closed, for example, with valves or plugs.
Many plugs are known and commercially available which can be run and locked into a well tubular so that it seals off the bore. Such plugs are typically run with a running tool which positions the plug in a plug receiving space of a bore, and then activates a locking mechanism which is integrated in the plug itself. The running tool thus has means for locking to the plug itself, and also means for operating the plug locking mechanism.
This can be a satisfactory solution for plugs where the sole technical object is to seal off a bore. However, many plugs, as well as other well bore components, contain other technical features beyond merely sealing off the bore. Indeed, as well technology matures, more technical functions may be embedded into such well bore components. Some well bore components may be installed for other technical purposes other than sealing off the bore.
Such technical functions in a well bore component requires space. Space consuming functionality can, for instance, be feedthroughs within a plug. One may, for example, need a large diameter feedthrough for supplying sufficient power to the pump when suspending an electrical submersible pump (ESP) from a plug locked in a production bore. One may also want to arrange other lines, such as control lines, through the plug, or even a through bore. The available size of the well tubular bore restricts the possible size and number of functions embedded in the plug.
In some cases, the well bore component can be a tubing hanger, installed within or below a Xmas tree. One then wants to maintain a large production bore through the tubing hanger while simultaneously embedding various functions within the tubing hanger body. As with a well plug, the available space within the tubing hanger body is partially governed by the space used for locking the tubing hanger in the wellhead assembly.